No abstract

With the increasing demand for multispectral information acquisition, infrared multispectral imaging technology that is inexpensive and can be miniaturized and integrated into other devices has received extensive attention. However, the widespread usage of such photodetectors is still limited by the high cost of epitaxial semiconductors and complex cryogenic cooling systems. Here, we demonstrate a noncooled two-color infrared photodetector that can provide temporal-spatial coexisting spectral blackbody detection at both near-infrared and mid-infrared wavelengths. This photodetector consists of vertically stacked back-to-back diode structures. The two-color signals can be effectively separated to achieve ultralow crosstalk of ~0.05% by controlling the built-in electric field depending on the intermediate layer, which acts as an electron-collecting layer and hole-blocking barrier. The impressive performance of the two-color photodetector is verified by the specific detectivity (D*) of 6.4 × 109 cm Hz1/2 W−1 at 3.5 μm and room temperature, as well as the promising NIR/MWIR two-color infrared imaging and absolute temperature detection.

No abstract

The ultrabroadband spectrum detection from ultraviolet (UV) to long‐wavelength infrared (LWIR) is promising for diversified optoelectronic applications of imaging, sensing, and communication. However, the current LWIR‐detecting devices suffer from low photoresponsivity, high cost, and cryogenic environment. Herein, a high‐performance ultrabroadband photodetector is demonstrated with detecting range from UV to LWIR based on air‐stable nonlayered ultrathin Fe3O4 nanosheets synthesized via a space‐confined chemical vapor deposition (CVD) method. Ultrahigh photoresponsivity (R) of 561.2 A W−1, external quantum efficiency (EQE) of 6.6 × 103%, and detectivity (D*) of 7.42 × 108 Jones are achieved at the wavelength of 10.6 µm. The multimechanism synergistic effect of photoconductive effect and bolometric effect demonstrates the high sensitivity for light with any light intensities. The outstanding device performance and complementary mixing photoresponse mechanisms open up new potential applications of nonlayered 2D materials for future infrared optoelectronic devices.

Uncooled infrared photodetectors have evoked widespread interest in basic research and military manufacturing because of their low‐cost, compact detection systems. However, existing uncooled infrared photodetectors utilize the photothermoelectric effect of infrared radiation operating at 8–12 µm, with a slow response time in the millisecond range. Hence, the exploration of new uncooled mid‐wavelength infrared (MWIR) heterostructures is conducive to the development of ultrafast and high‐performance nano‐optoelectronics. This study explores a van der Waals heterojunction on epitaxial HgCdTe (vdWs‐on‐MCT) as an uncooled MWIR photodetector, which achieves fast response as well as high detectivity for spectral blackbody detection. Specifically, the vdWs‐on‐MCT photodetector has a fast response time of 13 ns (77 MHz), which is approximately an order of magnitude faster than commercial uncooled MCT photovoltaic photodetectors. Importantly, the device exhibits a photoresponsivity of 2.5 A W‐1, quantum efficiency as high as 85%, peak detectivity of 2 × 1010 cm Hz1/2 W‐1 under blackbody radiation at room temperature, and peak detectivity of up to 1011 cm Hz1/2 W‐1 at 77 K. Thereby, this work facilitates the effective design of high‐speed and high‐performance heterojunction uncooled MWIR photodetectors.

Development of near-infrared (NIR) and shortwave infrared (SWIR) emitting fluorophores is central to the fluorescence-based bioimaging. While conjugated polymer nanoparticles (polymer dots) are one of the promising fluorophores for this application, obtaining polymer dots that show bright fluorescence, especially in the SWIR wavelength region, has been challenging. Here, we report generalized approach to obtain bright polymer dots through a systematic characterization of photophysical properties of NIR and SWIR emitting polymer dots. Detailed photophysical characterization of a series of polymer dots fabricated using polycarbazole (PCz)based conjugated polymers that adopt bent and twisted conformation reveals that the fluorescence brightness of the PCz-based polymer dots is determined by subtle balance between fluorescence quenching due to polymer chain interaction inside the particles and the twisting between the donor and acceptor moieties of the conjugated polymers inside the particles. Our results provide important insight into the rational design of highly fluorescing SWIR-emitting polymer dots.

No abstract

Abstract. The security of quantum key distribution (QKD) relies on the Heisenberg uncertainty principle, with which legitimate users are able to estimate information leakage by monitoring the disturbance of the transmitted quantum signals. Normally, the disturbance is reflected as bit flip errors in the sifted key; thus, privacy amplification, which removes any leaked information from the key, generally depends on the bit error rate. Recently, a round-robin differential-phase-shift QKD protocol for which privacy amplification does not rely on the bit error rate [Nature 509, 475 (2014)] was proposed. The amount of leaked information can be bounded by the sender during the state-preparation stage and hence, is independent of the behaviour of the unreliable quantum channel. In our work, we apply the tagging technique to the protocol and present a tight bound on the key rate and employ a decoy-state method. The effects of background noise and misalignment are taken into account under practical conditions. Our simulation results show that the protocol can tolerate channel error rates close to 50% within a typical experiment setting. That is, there is a negligible restriction on the error rate in practice.Practical round-robin differential-phase-shift quantum key distribution 2